Vane type hydraulic motor



v 9, 1948. J. K. DOUGLAS 2,453,309

VANE TYPE HYDRAULIC MOTOR Original Filed Dec. 29, 1959 2 Sheets-Sheet 195x as 95 97 a 67 66 INVENTDR JAMES K.DDUBL AS 69 70 I 7 6 77 79 4 53 7/84 56 4 7a 53 a5 ATTORNEY.

J. K. DOUGLAS VANE TYPE HYDRAULIC MOTOR Nov. 9, 194s.

2 Sheets-Sheet 2 Original Filed Dec. 29, 1939 INVENTUR Patented Nov. 9,1948 VANE TYPE HYDRAULIC MOTOR,

James K. Douglas, Shorewood, Wis., assignmto The Oilgear Company,Milwaukee, Wis, a corporation of Wisconsin Original application December29, 1939, Serial No. 311,479, now Patent No. 2,345,920, April 4, 1944.Divided and this application March 15, 1943, Serial No. 479,229

Claims. I 1

This application is a division of application Serial No. 311,479 whichwas filed December 29, 1939, and has since matured into Patent2,345,920.

The invention relates to a drive which includes a vane type hydraulicmotor and a control therefor.

An object of the invention is to provide a hydraulic drive having a vanetype motor, which is adapted to drive a load when supplied with motiveliquid, and a control for rendering the motor ineffective to drive theload regardless of whether or not the supply of motive liquid isdiscontinued.

Another object is to provide a hydraulic drive having a motor fordriving a load and means for rendering the motor ineffective to resistmovement of the load.

Other objects and advantages will appear from the following descriptionof an embodiment of the invention shown schematically in the accoxnpanying drawings in which the views are as follows:

Fig. 1 is a diagram or the hydraulic circuit of a drive in which theinvention is embodied.

Fig. 2 is a view showing a. control valve in a position different fromthat shown in Fig. i.

Fig. 3 is a view showing a pilot valve in a position different from thatshown in Fig. i.

Fig. 4 is a vertical longitudinal section through one of the motorsshown in Fig. l, the view being taken on the line ld of Fig. 5.

Fig. 5 is a. transverse section through the motor taken on the line 55of Fig. 4:.

Fig. 6 is a transverse section taken through the motor on the line t-6of Fig. s.

Fig. 7 is a transverse section through the mo tor taken on the line ll-lof Fig. 4.

Fig. 8 is a vertical section taken on ular lines 9-8 of Figs. 5 and 7.

For the purpose of illustration, the invention has been shown embodiedin a drive for a ma chine of the type having a carriage which makes anidle stroke in one direction at high speed and a working stroke in theopposite direction at a lower speed appropriate for a tool to operateupon a work piece but it is to be understood that the invention isadapted to various other uses.

The machine includes a carriage i having a rack 2 fixed upon the underside thereof and in mesh with a gear 9 which is fixed upon a shaft l sothat rotation of shaft 9 in one direction or the other will causecarriage i to move in one the urea direction or the other. Since themachine per se forms no part of the present invention, all other partsthereof have been omitted from the drawing.

2 Shait ii is adapted to be rotated by two vane type hydraulic motors 8and 3- which are. com nested thereto by suitable drives 8 and i respecwlively. Motors 5 and 5 are energized byapi mp 8 which delivers liquid toboth motors tocause. them to move carriage i in one direction at acutting speed and then delivers its entire output to motor 5 only tocause it to move carriage l at high speed in the opposite direction. atwhich time motor 5 is short circuited and the. vanes thereof areretracted so that its rotor. spins idly as presently will be explained.

The two motors may be of the same sizebut' motor 5 has been shown asbeing larger than motor 5 in order to obtain a high speed oi car riage 8during its return stroke. For example, if the displacement of motor 5 istwice that oi motor 5, carriage i will be moved during its idle strokeat a speed three times its speed during its working stroke. I

Motor 5 may be of the type shown in Figs. a to 8 and motor 5 may beexactly the same except that it may he of a different size if desired.its shown, the motor includes a rotor l9 ireyed upon a shaft 9 i andarranged within a stator consisting primarily of a casing it which has aremovable end head it and rotatably supports shaft ll by means ofbearings it and i5, a spacer ring iii which is arranged within casing 82and extends around rotor it, and two cheek plates ill and it which arearranged within casing 82 upon opposite sides of spacer ring it, thecheek plates and spacer ring being clarnlpeciin position by end head itand spacer ring it being just enough thicker than rotor it to permitrotor 69 to turn freely between cheek plates it and i9. 7

The inner peripheral surface of spacer ring it provides a track 69 for aplurality oivanes it.

which are the same width as rotor iii and fitted in slots formedradially therein. Vane track it? is approximately elliptical with itsshort. diameter horizontal and Just enough greater than the diameter oirotor it to permit rotor it to turn free is. The vertical diameter oftrack 99 is enough greater than the diameter of rotor ill; to provide aworking chamber 2i of the desired size both above and below rotor i9.

Each chamber 2i communicates with two ports 22 and 23 which are arrangedupon opposite sides 05, the vertical center line of track M with the twoports 22 arranged diametrically opposite each other and each port 23spaced approximately 90 from ports 22. Each portion of track l9 betweenadjacent ends of adjacent ports forms a sealing are which is ordinarilyconcentric with rotor I.

formed in the end wall of easing l2 and com-- municates with a main port25 by means ofwhich .the motor may be connected to one side of ahydraulic circuit, and ports 23 communicate with a passage 28 which isformed in the end wall of casing l2 outward from passage 24 andcommunicates with a main port 21 by means of which the motor may beconnected to the other side of the hydraulic circuit.

The arrangement is such that, when main port is connected to thedischarge outlet of a pump or other source of motive liquid and mainport 21 is connected to a return or dischargeline so that ports 22function as inlet ports and ports 23 function as discharge ports. themotive liquid entering through each port 22 will exert a force upon theouter portion of that vane which is adjacent the end of port 22 and incontact with the sealing arc of vane track it. The force exerted by theliquid upon that vane will cause rotor ill to rotate in acounterclockwise direction in respect to Fig. 5 and the liquid will actupon each succeeding vane as it passes the end of 'port 22 and comesinto contact with the sealing arc so that rotor I0 is caused to rotatecontinuously as long as motive liquid is supplied to port 25. The liquidahead of each vane will be discharged into the adjacent port 23 as soonas the preceding vane passes e adjacent end of that port 23. When motiveliquid is supplied to port 21, the motor will operate in exactly thesame manner but in the opposite direction.

It is essential that the vanes just beyond the ends of the inlet portsbe held in contact with vane track i9 as otherwise the liquid could flowfreely from each inlet port to a discharge port and no rotative forcewould be transmitted to rotor l0. These vanes may be held in contactwith track is by subjecting the inner ends thereof to a pressure higherthan the pressure prevailing at the inlet ports but, if the inner endsof the vanes were subjected to this higher pressure during a completerevolution of rotor l0, each vane would exert such an excessive forceagainst track l9 during the time its outer end was exposed to the low ornegative pressure of the discharge liquid that undue wear of the vanesor tracks might result.

In order to hold the working vanes agains the vane track and at the sametime to avoid excessive wear of the vanes or tracks, the vanes have theinner ends thereof subjected to a pressure higher than the pressure ofthe motive liquid only during the time the outer ends thereof aresubjected to the pressure of the motive liquid.

As shown, cheek pates l1 and it are each provided with a pair of arcuatepressure grooves 3|, which are arranged diametrically opposite eachother and spaced radially inward from ports 22: and a pair of arcuatepressure grooves 22 which are arranged diametrically opposite each otherand spaced radially inward from ports 23, the pressure grooves beingspaced a predetermined distance apart and so located that the inner endsof each vane slot will register with the four grooves successively asrotor ll rotates.

As shown in m. e, the two grooves 1| in that plate II are connnected toeach other by a passage which is formed in cheek plate l1 andcommunicates with a connector 24 carried by end'head It, and the twogrooves 22 in cheek plate i! are connected to each other by a passagewhich is formed in cheek plate i1 and communicates with a connector 80carried by end head II. The pressure grooves in cheek plate Itcommunicate with the corresponding pressure grooves in cheek plate ilthrough the inner ends of the vane slots and are provided for thepurposes of hydrostatic'ally balancing rotor ii.

As previously explained, motor I is exactly the same as motor I exceptthat ity is larger. Consequently, the main ports and the connectors of aboth motors have been indicated in Fig. l by the same reference numeralsbut with the exponent added to the reference numerals applied to motorI.

The liquid for operating motors I and I is discharged by pump 8 into achannel-40 and the liquid discharged by motors I and I is returned toDump 8 through a channel 4!. In order to make up for leakage losses andto supercharge pump 8, additional liquid is supplied to channel 4| by agear pump 42 which draws liquid from a reservoir 43 and discharges itinto a channel 44 through which it supplies liquid to a valve operatingmechanism to be presently described.

The liquid discharged by gear pump 42 in excess of the liquid requiredto operate the valve mechanism is exhausted through a resistance v valve45 into one end of a channel 4! the other end of which is connected tochannel 41. The liquid discharged by gear pump 42 into channel 48 inexcess of the liquid required to supercha'rge pump a is exhaustedthrough a relief valve 41 into reservoir 42. Gear pump 42 is thusenabled to maintain in channel 4| a pressure equal to the resistance ofvalve 41 and to maintain in channel 44 a pressure equal to the sum ofthe resistances of valves 45 and 41.

Pump 8 is initially controlled by a start and stop valve 48 which isfitted in the bore of a valve casing as having three annular grooves orports 50, 6i and 52 formed therein. Port ll communicates with channel40, port it com- 54 through which liquid is returned from the motors.

The arrangement is such that, when valve 42 is in the position shown inFig. 1, liquid discharged by pump I will flow through channel 40 andvalve casing 4! into channel It and the liquid returned from the motorsthrough channel 54 will now through port I2 and channel 4! to pump 8.when valve 48 is shifted to the limit of its movement toward the left,it will block port I and open port 52 to port so that pump 2 isbypassed.

The inner and outer end of each vane may be subjected to the samepressure and each vane held in contact with track I. by a light springarranged in the inner end of its vane slot in the well known manner butthe working vanes are preferably urged against the vane track by liquidhaving a pressure related to but somewhat higher than the pressure oithe motive liquid.

As shown, liquid for holding the working vanes 20 of motors] andvagainst vane tracks I2 is supplied by a small capacity pump II which isdriven in unison with pump 8 and draws liquid from channel 53 anddischarges it into a channel 56. The liquid discharged by pump 55 inexcess of the volume required to hold the working vanes outward isexhausted through a low pressure resistance valve 51 back into channel53 so that the pressure in channel 56 is always a, few pounds higherthan the pressure created by pump 8.

Motors 5 and 5"- are controlled by a plurality of valves which aresimultaneously operable to control the fiow of liquid to and fromthe-main ports of the motors and the flow of liquid to and from thepressure grooves of the motors. As shown, six valves or pistons 6|, 62,63, 64, 65. and 66 are fixed upon a plunger 61 and closely fitted in thebore of a control valve casing 60 having twelve annular grooves or ports69, 10, 1|, 12, 13, 14, 15, 16, 11, 18, 19 and 80 formed therein.

Port 69 is connected by a channel 8| to port 21 of motor 5 and to port21 of motor 5, and channel 54 is connected to the left end of the boreof valve casing 68 so that ports 21 and '21 are connected to the intakeof pump 8 when valve plunger 61 is in the position shown in Fig. 1. Port10 is connected by a channel 82 to port 25 of motor 5 and it has channel53 connected thereto so that port 25 is at all times subjected to thepressure created by pump 8.

Port 1| is connected by a channel 83 to port 25 of motor 5, ports 12 and16 are connected by a channel 84 to channel 54 intermediate the endsthereof, port 13 is connected by a channel 85 to connector 36 on motor5, port 14 has channel 56 .connected thereto, port 15 is connected by achannel 86 to connector 34 on motor 5, port 11 is connected by a channel81 to connector 36' on motor 5, port 18 and the right end of the bore ofvalve casing 68 are connected to a drain channel 88 which dischargesinto reservoir 43, port 19 is connected by a channel 89 to connector 34*on motor 5*, and port 80- is connected by a channel 90 to channel 56intermediate the ends thereof.

Valve plunger 61 is adapted to be shifted in one direction or the otherby a piston 9| which is connected thereto and fitted in a cylinder 92arranged upon the right end of valve casing 68. Liquid for operatingpiston 9| is supplied to cylinder 92 under the control of a pilot valve93 which is arranged in the bore of a valve casing 94 having both endsthereof connected to drain channel 88 so that movement of valve 93 willnot be hampered by entrapped liquid or gas.

Valve casing 94 has three annular grooves or ports 55, 36 and 91 formedin the wall of the bore thereof. Port 95 has gear pump channel 44connected thereto, port 96 is connected by a channel 98 to the right endof cylinder 92, and port 91 is connected by a channel 99 to the left endof cylinder 92.

Pilot valve 93 may be shifted inany suitable manner such'as in responseto carriage approaching the limit of its movement in each direction.Means are provided to compensate for the over run of carriage i but,since such means are well known and form no part of the presentinvention, they have been omitted from the drawing and valve 93 shown ashaving its stem connected by a link I00 to a lever |0l which has one ofits ends pivoted upon a bracket |02 and its other end extending into thepath of two dogs I03 and I04 carried by carriage i.

Operation Assuming that the several parts are in the positions shown inFig. 1 and that pumps 3, 42 and 55 are running, the drive will functionas follows:

Gear pump 42 will draw liquid from reservoir 43 and discharge it throughchannel 44 and resistance valve 45 into channel 45. The liquiddischarged by gear pump 42 in excess of the liquid required tosupercharge pump 8 will be exhausted through relief valve 41 intoreservoir 43 so that gear pump 42 maintains a low or return pressure inchannel 46 and a higher or gear pump pressure in channel 44. The gearpump pressure will extend from channel 44 through pilot valve casing 94and channel 90 to the left end of servomotor cylinder 92 and causepiston 9| to hold control valve plunger 61 in the position shown inFig. 1. The return pressure will extend from channel 46 through channel4|, valve casing 49 and channel 54 to the left end of valve casing 68and from channel 54 through channel 84 to ports 12 and 16.

Main pump 8 will discharge liquid through channel 40, valve casing49 andchannel 53 to port 10 in control valve casing 68 and maintain therein atall times a pressure proportional to the load on pump 8.

Pump 55 will draw liquid from channel 53 and discharge a part of itthrough resistance valve 51 back into channel 53 so that pump 55 iscaused to maintain in channels 56 and 90 and in ports 14 and asuperpressure which is always greater than the main pump pressure by anamount equal to the resistance of valve 51.

With control valve plunger 61 in the position shown in Fig. 1, port 15is open to port 14 and port 19 is open to port 80 so that superpressurecan extend from port 14 through port 15, channel 86, connector 34 andpassage 33 (Fig. 6) to the pressure grooves 3| in motor 5 and from port80 through port 19, channel 89, connector 34 and passage 33 to thepressure grooves 3| of motor 5.

Port 13 is open to port 12 and port 11 is open to port 15 so that returnpressure can extend from port 12 through port 13, channel 85, connector36 and passage 35 (Fig. 6) to the pressure grooves 32 of motor 5 andfrom port 15 through port 11, channel 81, connector 36 and passage 35 tothe pressure grooves 32 of motor 5.

Port 69 is open to return channel 54 so that return channel 54 isconnected through valve casing Eli, channel as, main ports 21 and 21 andpassages 26 (Fig. 7) to the ports 23 of both motors.

Port H is open to port 10 so that motive liquid will flow throughchannels 83 and 82, main ports 25 and 25 passages 26 and ports 22 to thepressure sides of the chambers 2| (Fig. 5) of both m0- tors.

The pressure of the motive liquid tends to move inward the vanes 20whose outer ends extend into the pressure sides of the chambers 2| butthe inner ends of those vanes are subjected to the superpressure ingrooves 3| which holds them firmly against vane track l9 so that themotive liquid may act upon the outer end portions thereof and causerotors W to rotate in a counterclockwise direction, the liquid carriedacross the sealing arcs of track I9 by the vanes being discharged intoports 23 and returned through the above described channels to the intakeof pump 8.

Each vane 20 is held by the superpressure firmly against track I9 untilthe inner end of its slot moves out of registry with groove 31 at whichtime it has moved part way across the sealing arc, then the liquid inthe inner end of the vane slot is trapped therein during movement of thevane through a slight angular distance and then the inner end of theslot registers with a groove 32 which contains liquid at the returnpressure, as previously explained, so that the vane is hydrostaticallybalanced and is held against the vane track solely by centrifugal force.

Rotation of rotors I in a counterclockwise direction causes drives 6 andI to rotate shaft 4 in a counterclockwise direction and thereby causegear 3 to move rack 2 and carriage I toward the left at a speedproportional to the displacement of pump 8 relative to the combineddisplacements of motors and 5.

As carriage I approaches the limit of its movement toward the left, dogI04 will engage lever llil and cause it to shift pilot valve 93 to theposition shown in Fig. 3, provision being made for over run of carriageI as mentioned above. Liquid from ear pump 42 will then flow throughchannel 44, valve casing 94 and channel 98 to the right end of cylinder92 and cause piston 9| to shift control valve plunger 61 to the positionshown in Fig. 2, the liquid expelled from cylinder 92 by piston 9| beingconducted through channel 99, valve casing 94 and drain channel 88 intoreservoir 43.

Shifting control valve plunger 61 to the position shown in Fig. 2connects port 69 to port Hi and pump pressure will extend from port I 10through port 69 and channel 8| to main port 21 of motor 5 and to mainport 21 of motor 5, and pressure will extend from port 10 throughchannel 82 to main port 25 of motor 5 so that motor 5 is short circuitedand the outer ends of all of the vanes thereof are subjected to pumppressure. Also, port 80 is blocked and ports 11 and 19 are open to port18 so that all of the pressure grooves 3| and 3 2 of motor 5 areconnected to drain channel 88 through the previously described channels.Since all of the vanes of motor a have their outer ends subjected topump pressure and their inner ends to zero pressure, they will be movedinward so that, when motor 5- is driven by motor 5 as will presently beexplained, rotor Iii of motor 5 will spin idly and without displacingany liquid.

While motor 5 has been shown as having both of its main ports connectedto the pressure side of the main circuit and all of its pressure groovesconnected to drain for the purpose of forcing the vanes inward, thevanes could be forced inward by connecting both main ports to the returnside of the circuit and all of the pressure grooves to drain or byconnecting both main ports to the pressure side of the circuit and allof the pressure grooves to the return side of the circuit.

When control valve plunger is in the position shown in Fig. 2, port 13is open to port 14 instead of to port 72 and port 15 is open to port 16instead of to port 14, so that the pressures in the pressure grooves ofmotor 5 are reversed, and port 1| is open to port I2 instead of to port10 and port 69 is open to port 10 instead of to return channel 54 sothat the flow of motive liquid to motor 5 is reversed. Consequently,motor 5 will operate in the previously described manner but in theopposite direction and move carriage I toward the right at a high speedwhich is'proportional to the displacement of motor 5 relative to thedisplace- 8 ment of pump 8. During movement of carriage I toward theright, drive 1 will rotate rotor ll! of motor 5 which will spin idlysince its vanes are fully retracted as previously explained.

As carriage I approaches the limit of its movement toward the right, dogI03 will engage lever IBI and cause it to shift pilot valve 93 to theposition shown in Fig. 1, provision being made for over run of carriageI as mentioned above. Liquid from gear pump 42 will then flow throughchannel 44, valve casing 94 and channel 99 to the left end of cylinder92 and cause piston 9| to shift control valve plunger 61 to the positionshown in Fig. 1, the liquid expelled from cylinder 92 by piston 9| beingconducted through channel 98, valve casing 94 and drain channel 88 toreservoir 43.

Shifting control valve plunger to the position shown in Fig. 1 completesa cycle of operation and starts a second cycle of operation as explainedabove.

The drive described herein is susceptible of various modifications andadaptations without departing from the scope of the invention which ishereby claimed as follows:

1. The combination, with a, hydraulic motor having a vane track and arotor arranged within said track and provided with a plurality of vanesfor engaging said track, of means for directing motive liquid betweensaid track and said rotor, means for causing each of said vanes toengage said track during at least a part of each revolution of saidrotor to thereby enable said liquid to act upon said vanes and rotatesaid rotor, and means for causing all of said vanes to move inward outof engagement with said track and thereby prevent liquid directedbetween said track and said rotor fro-m rotating said rotor.-

2. The combination, with a, hydraulic motor having a vane track and arotor arranged within said track and provided with a plurality of vanesfor engaging said track, of means for directing motive liquid betweensaid track and said rotor, the pressure of said liquid acting upon theouter ends of said vanes and tending to move them inward away from saidtrack, means for supplying to the inner end of each vane during at leasta part of each revolution of said rotor liquid at a pressure greaterthan the pressure of said motive liquid to thereby hold said vanesagainst said track and enable said motive liquid to rotate said rotor,and means for reducing the pressure at the inner ends of said vanesbelow thepressure of said motive liquid to thereby cause said vanes tomove inward cut of engagement with said track and prevent said motiveliquid from rotating said rotor,

3. In a drive, the combination of a hydraulic motor having a vane trackand a rotor arranged within said track and provided with a plurality ofvanes for engaging said track, said motor having an inlet for directinliquid between said track and said rotor and an outlet for the dischargeof liquid therefrom, means for supplying motive liquid to said motor toenergize the same, the pressure of said liquid acting upon the outerends of said vanes and tending to move them inward, means for supplyingto the inner end of each vane during at least a part of each revolutionof said rotor liquid at a pressure related to and greater than thepressure of said motive liquid to thereby hold said vanes against saidtrack and enable said motive liquid to rotate said rotor, and means forreducing the pressure at the inner end of each vane below the pressureat the outer to said motor to act upon the outer portions oi" said vanesand effect rotation of said rotor, and means for causing said vanes tomove out of contact with said track and out of the path oi said liquidto thereby prevent said rotor from being rotated by the liquid suppliedto said motor.

5. In a hydrodynamic machine, the combination of a cylindrical rotor, astationary endless vane track arranged around said rotor and form ingspaces of varying widths between it and the periphery of said rotor,casing means enclosing said rotor and said track and providing portswhich communicate with said spaces, a plurality of approximately radialvanes slldable in said rotor and adapted during rotation of said rotorto continuously engage said track and provide seals between said portsso that rotation of said rotor will cause liquid to be transferred fromone to another of said ports and motive liquid supplied to a port willcause rotation of said rotor, and means for preventing transfer ofliquid from one port to another in response to rotation of said rotorand for preventing rotation of said rotor in response to motive liquidbeing supplied to a port.

6. The combination, with a hydraulic motor having a vane track and rotorarranged within said traclr and provided with a plurality of vanes forengaging said track, of means for directing motive liquid between saidtrack and said rotor including a valve for controlling the delivery ofsaid liquid, means for supplying to the inner end of each vane during atleast a part of each revolution of said rotor liquid at a pressuregreater than the pressure of said motive liquid to thereby hold saidvanes against said track and enable said motive liquid to rotate saidrotor including a valve operable to discontinue the supply of highpressure liquid to the inner ends of said vanes and to connect saidinner ends to exhaust to cause said vanes to be moved inward by thepressure of the motive liquid and thereby prevent said motive liquidfrom rotating said rotor, and means for simultaneous'y operating saidvalves.

7. In a hydraulic drive for driving an element, the combination of ahydraulic motor having a vane track and a rotor adapted to be connectedto said element and arranged within said track and provided with aplurality of substantially radial vane slots having vanes fitted thereinand adapted to engage said traclr, said motor having formed therein apassage with which the inner end of each vane slot communicates during apart of each revolution of said rotor, means for directing motive liquidto the outer ends of said vanes to rotate said rotor and thereby drivesaid element, the pressure of said motive liquid acting upon said vanesat the outer ends thereof and tending to move them inward, a source ofliquid having a pressure higher than the pressure of said motive liquid,channel means for directing liquid from said source to said passage tothereby hold said vanes against said track and enable said motive liquidto rotate said rotor, and valve means associated with said channel meansfor redill i0 ducing the pressure in said passage below the pressure ofsaid motive liquid to cause said vanes to be moved inward by thepressure at the outer ends thereof and thereby prevent said motiveliduid from rotating said motor.

8. In a hydraulic drive for driving an element, the combination of ahydraulic .motor having a vane track and a rotor adapted to be connectedto said element and arranged within said tract; and provided with aplurality of substantially radial vane slots having vanesfltted thereinand adapted to engage said traclr, said motor having formed therein apassage with which the inner end of each vane slot communicates during apart or" each revolution of said rotor, means for directing motiveliquid to the outer ends of said vanes to rotate said rotor and therebydrive said element, the pressure of said motive liquid act ing upon saidvanes at the outer ends thereof and tending to move them inward, asource of liquid having a pressure higher than and varying in accordance with variations in the pressure of said motive liquid, channelmeans for directing liquid from said source to said passage to therebyhold said vanes against said track and enable said mo tive liquid torotate said rotor, and valve means associated with said channelmeans forreducing the pressure in said passage below the pressure of said motiveliquid to cause said vanes to be moved inward by the pressure at theouter ends thereof and thereby prevent said motive liquid from rotatingsaid rotor.

9. In a hydraulic drive for driving an element, the combination oi ahydraulic motor having a vane track and a rotor adapted to be connectedto said element and arranged within said tracl-z and provided with aplurality of substantially radial vane slots having vanes fitted thereinand adapted to engage said track, said motor having formed therein a endof each vane slot communicates during a part oi. each revolution of saidrotor, means for directing motive liquid to the outer ends of said vanesto rotate said rotor and thereby drive said element, the pressure ofsaid motive liquid acting upon said vanes at the outer ends thereof andtending to move them inward, a source of liquid having a pressure higherthan the pressure of said motive liquid, channel means for directingliquid from said source to said passage to thereby hold said. vanesagainst said track and enable said motive liquid to rotate said rotor,valve means associated with said channel means for reducing the pressureinsaid passage below the pressure of said motive liquid to cause saidvanes to be moved inward. by the pressure at the outer ends th'ereoi andthereby prevent said motive liquid from rotating said rotor, and meansre sponsive to said element reaching a given point in its movement foroperating said valve means.

is. In a drive, the combination with a hy draulic motor having a vanetrack and a rotor arranged within said traclr and provided with aplurality of vanes to engage said track, or pres sure channels fordirecting motive liquid to said motor at the outer ends of said vanes toenergize said motor, said motive liquid acting upon the outer ends ofsaid vanes and tending to move said vanes inward away from said traclr,a booster pump having its inlet connected to said pressure channel, aresistance valve connected between the outlet of said booster pump andsaid pressure channel, said booster pump being adapt- 1 ed to drawliquid from said pressure channel and deliver a part thereof to theinner ends of said passage with which the inner it and saidyanes, a lowpressureehonnebfm yalve means tor connecting the inend; a: 'eaid vanesto said booster pump and to sale pregame channel selectively.

' J K. DOUGLAS.

emcee man ale-onus e.

Number 12 UNITED STATES PATENTS Home Date Noah Aug. 11, 1908 WilliamsJune 16, 1914 Seven July 25, 1916 Root Oct. 5, 1920 Thomas Feb. 9, 1926Thomas "Aug. 8, 1933 Klimek Sept. 19, 1933 Petroni et a1. Dec.,26, 1933Kendrick Sept. 16, 1941

